Madecassoside, a triterpenoid saponin compound mainly
isolated
from the gotu kola herb (Centella asiatica), shows an extensive range of biological activities, including antiapoptotic,
antioxidant, anti-inflammatory, moisturizing, neuroprotective, and
wound healing effects. It has been highly used in the management of
eczema, skin wounds, and other diseases. Due to poor oral bioavailability,
membrane permeability, and intestinal absorption, the clinical application
of the madecassoside is limited. Hence, a drug carrier system is needed
that not only sustains the release of the madecassoside but also overcomes
the drawbacks associated with its administration. Therefore, the authors
prepared novel pH-responsive chitosan-based nanogels for the sustained
release of madecassoside. Free radical polymerization technique was
used for cross-linking of polymer chitosan and monomer methacrylic
acid in the presence of cross-linker N′,N′-methylene
bis(acrylamide). The decrease in polymer crystallinity after polymerization
and development of nanogels was demonstrated by XRD and FTIR analysis.
The effects of nanogel contents on polymer volume, sol–gel
analysis, swelling, drug loading, and release were investigated. Results
indicated that high swelling and maximum release of the drug occurred
at pH 7.4 compared to pH 1.2 and 4.6, indicating the excellent pH-sensitive
nature of the engineered nanogels. High swelling and drug release
were perceived with the integration of a high quantity of chitosan,
while a decline was observed with the high integration of N′,N′-methylene
bis(acrylamide) and methacrylic acid contents. The same effects of
nanogel contents were shown for drug loading too. Sol fraction was
reduced, while gel fraction was enhanced by increasing the chitosan
load, N′,N′-methylene bis(acrylamide), and methacrylic
acid. The Korsmeyer–Peppas model of kinetics was trailed by
all nanogel formulations with non-Fickian diffusion. The results demonstrated
that prepared nanogels can be employed for sustained release of the
madecassoside.